The antennae themselves don't do the sensing, it's the sensory cells on the antennae, and sensory cells can also occur on legs, feet, mouthparts, genitalia, and other organs. Sensory cells may be chemoreceptors, mechanoreceptors (including proprioceptors), or photoreceptors. I suppose that in some insects like monarch butterflies there are also magnetoreceptors.
No... there are a variety of sensory apparatus in insects. From tympanic membrances, to any hair (bristles) that can vibrate, to compound eyes and simple eyes. Not to mention a keen sense of odor as well. You have only scratched the surface of the sensory inputs/structures of a very successful group of animals.
Are antennas the only things that feel, see, hear, etc. on a bug? If not, what are their purpose? And without them is the bug pretty much unconscious?
